Mendosoma lineatum, the telescope fish, is a species of trumpeter native to the subantarctic and cooler temperate waters of the Southern Ocean. It inhabits tide pools and surge channels and has been found living inside such invertebrates as salps. It occurs from near the surface to a depth of about 20 metres (66 ft). This species can reach a length of 40 centimetres (16 in) TL. This species is the only known member of its genus.